JP2013040880A - Charge control device for secondary battery and charge control method for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge control device for secondary batteries reducing the speed of storage deterioration by taking account of associated characteristics between a storage charge level and storage deterioration.SOLUTION: A secondary battery 1 shows such characteristics that, in a first area where a storage charge level exceeds 70%, an electric energy ratio after the storage to that before the storage is substantially overlapped on a straight line A, while in a second area where the storage charge level is less than 70%, the same electric energy ratio is substantially overlapped on a straight line B. The inclination of the straight line B is substantially 1/7 of the inclination of the straight line A so as to significantly reduce the deterioration speed in the stored state, when the storage charge level is less than 70%. The charge control device is configured to selectively charge between a charge level where the storage charge level exceeds 70% and a charge level where the storage charge level is less than 70%.

Description

  The present invention relates to a secondary battery charge control technique.

Secondary batteries such as lithium ion secondary batteries, nickel hydride secondary batteries, and nickel cadmium secondary batteries have been rapidly spreading in recent years as power sources for hybrid vehicles and electric vehicles.
A secondary battery used as a power source for an automobile is usually mounted on a vehicle in a battery module in which a plurality of secondary batteries are connected in series with a bus bar.
The secondary battery deteriorates by repeatedly charging and discharging, but storage deterioration occurs even in the storage state.
If the secondary battery deteriorates due to repeated charging and discharging or long-term storage, the so-called full charge capacity for charging the secondary battery 100% is reduced.
When the full charge capacity is reduced and the required discharge capacity becomes smaller than a predetermined value, the life of the secondary battery is reached.

The following method is known as an example of a method for extending the life of the secondary battery.
When the secondary battery is always fully charged, the chargeable capacity of the secondary battery is reduced at a predetermined rate due to deterioration over time. Therefore, the charging depth of the secondary battery in the initial state is limited to 80%. The discharge amount of the secondary battery is monitored, and when the charging time comes, the full charge capacity in a state where the secondary battery is deteriorated and reduced is registered and updated as a new full charge capacity. And the charge depth corresponding to this new full charge capacity is predetermined, and a secondary battery is charged to this charge depth. This charge / discharge cycle is repeated. According to this method, the aging deterioration of the secondary battery is suppressed by setting the charging depth in the initial state to 80% of the full charge, and the battery life is extended (for example, see Patent Document 1).

JP 2001-15590 A

  In the method described in Patent Document 1, the charging depth in the initial state is set to 80% of the full charge, and at the time of subsequent charging, a predetermined depth is set for a new full charge capacity after discharging. To charge. In this method, it is not considered that the aging of the secondary battery in the storage state changes depending on the charging depth.

The secondary battery charge control device of the present invention includes a first charge level region in which a change in the deterioration rate in the storage state with respect to a change in the charge level in the increasing direction is large, and a change in the charge level in the increasing direction. Is a charge control device that charges a secondary battery having a second charge level region in which the change in the deterioration rate in the storage state in the storage state is smaller than the first charge level region, Charging that selects one of a first charging level that has an upper limit value of the charging level that is full charging and a second charging level that belongs to the second charging level region and whose upper limit value of the charging level is lower than the full charging Level selection means, charge level detection means for detecting the charge level of the secondary battery, and charge control means for charging up to the upper limit value of each charge level selected by the charge level selection means. The features.
In addition, the secondary battery charge control method of the present invention includes a first charge level region in which the change in the deterioration rate in the storage state with respect to the change in the charge level in the increasing direction is large, and the charge level in the increasing direction. A charge control method for charging a secondary battery having a second charge level region in which the change in the deterioration rate in the storage state with respect to the change in the storage state is smaller than the first charge level region, the first charge level One of the first charge level belonging to the region and the upper limit value of the charge level being fully charged and the second charge level belonging to the second charge level region and the upper limit value of the charge level being less than full charge is selected A second step of detecting a charge level of the secondary battery, and a third step of charging up to an upper limit value of each charge level selected by the charge level selection means. The features.

  According to this invention, the change in the increasing direction of the deterioration rate in the storage state with respect to the change in the increasing direction of the charging level with respect to the first charging level in which the upper limit value of the charging level is fully charged is more Therefore, it is possible to select any one of the small second charge levels, thereby suppressing the storage deterioration of the secondary battery and extending the life.

Sectional drawing as one Embodiment of the secondary battery used for the charge control apparatus of the secondary battery which concerns on this invention. FIG. 2 is an exploded perspective view of the secondary battery shown in FIG. 1. The characteristic view which shows the relationship between the electric energy ratio which can be taken out before and after a preservation | save, and each preservation | save charge level. The characteristic view which shows the relationship between the electric energy ratio which can be taken out before and after a preservation | save in the case of 100% charge, and each preservation | save charge level. The characteristic view which shows the relationship between the travel distance of the vehicle carrying the secondary battery preserve | saved at the predetermined | prescribed charge level, and each preservation | save charge level. The characteristic view which shows the relationship between the mileage of the vehicle carrying the secondary battery of the state charged 100% after preserve | saving to a predetermined | prescribed charge level, and each preservation | save charge level. The block circuit diagram as one Embodiment of the charge control apparatus of the secondary battery of this invention. The processing flowchart as one Embodiment of the charge control method of the secondary battery of this invention.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is an enlarged cross-sectional view showing an embodiment of a cylindrical secondary battery applicable to the secondary battery charge control device of the present invention.
The cylindrical secondary battery 1 is, for example, a lithium ion secondary battery. In the secondary battery 1, each component for power generation described below is housed in a battery container composed of a cylindrical battery can 2 and a hat-type battery lid 3 that seals the upper portion of the battery can 2. The nonaqueous electrolytic solution 5 is injected.

The cylindrical battery can 2 is made of, for example, iron (SPCC), and nickel plating is applied to both the inner and outer surfaces. In the battery can 2, a groove 2 a protruding to the inside of the battery can 2 is formed on the opening 2 b provided on the upper end side.
An electrode group 10 is disposed inside the battery can 2. The electrode group 10 includes a cylindrical shaft core 15 having a hollow portion along the axial direction, and a positive electrode and a negative electrode wound around the shaft core 15 via a separator.

FIG. 2 is an exploded perspective view of the secondary battery 1 shown in FIG.
As shown in FIG. 2, the electrode group 10 has a structure in which a positive electrode 11, a negative electrode 12, and a separator 13 are wound around an axis 15. The outermost periphery of the electrode group 10 is wound so as to be the negative electrode 12 and the separator 13 on the outer periphery thereof. A side edge of the outermost separator 13 is fixed to the inner separator 13 by an adhesive tape 19.

  The positive electrode 11 includes a positive electrode metal foil that is formed of an aluminum foil and has a long shape, and a positive electrode mixture treatment portion 11a in which a positive electrode mixture is applied to both surfaces of the positive electrode metal foil. The upper side edge extending in the longitudinal direction of the positive electrode metal foil is a positive electrode mixture untreated portion where the positive electrode mixture is not applied and the aluminum foil is exposed. A number of positive electrode tabs 16 protruding in parallel with the axial direction of the shaft core 15 are integrally formed at equal intervals in the positive electrode mixture untreated portion.

  The positive electrode mixture includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder. The positive electrode active material is preferably lithium oxide. Examples include lithium cobaltate, lithium manganate, lithium nickelate, lithium composite oxide (lithium oxide containing two or more selected from cobalt, nickel, and manganese). The positive electrode conductive material is not limited as long as it can assist transmission of electrons generated by the occlusion / release reaction of lithium in the positive electrode mixture to the positive electrode. However, good characteristics can be obtained by using a lithium composite oxide composed of lithium cobaltate, lithium manganate, and lithium nickelate, which is the above-mentioned material.

The positive electrode binder can bind the positive electrode active material and the positive electrode conductive material, and can bind the positive electrode mixture and the positive electrode current collector, and must be significantly deteriorated by contact with the non-aqueous electrolyte 5. There are no particular restrictions. Examples of the positive electrode binder include polyvinylidene fluoride (PVDF) and fluororubber. The formation method of the positive electrode mixture treatment part 11a by the positive electrode mixture is not limited as long as the positive electrode mixture is formed on the positive electrode metal foil. As an example of a method of forming the positive electrode mixture processing portion 11a by the positive electrode mixture, a method of applying a dispersion solution of constituent materials of the positive electrode mixture on the positive electrode metal foil can be mentioned. By producing by such a method, a positive electrode mixture having excellent characteristics can be obtained.
An example of the coating thickness of the positive electrode mixture is about 40 μm on one side.

  The negative electrode 12 includes a negative electrode metal foil that is formed of a copper foil and has a long shape, and a negative electrode mixture treatment portion 12a in which a negative electrode mixture is applied to both surfaces of the negative electrode metal foil. The lower side edge extending in the longitudinal direction of the negative electrode metal foil is a negative electrode mixture untreated portion where the negative electrode mixture is not applied and the copper foil is exposed. In this negative electrode mixture untreated portion, a large number of negative electrode tabs 17 extending in parallel to the axial direction of the shaft core 15 and in the direction opposite to the positive electrode tab 16 are integrally formed at equal intervals. Yes.

The negative electrode mixture includes a negative electrode active material, a negative electrode binder, and a thickener. The negative electrode mixture may have a negative electrode conductive material such as acetylene black. As the negative electrode active material, it is preferable to use graphitic carbon, particularly artificial graphite. By using graphite carbon, a lithium ion secondary battery for a plug-in hybrid vehicle or an electric vehicle requiring a large capacity can be manufactured. The formation method of the negative electrode mixture treatment part 12a by the negative electrode mixture is not limited as long as the negative electrode mixture is formed on the negative electrode metal foil. However, among them, a negative electrode mixture having excellent characteristics can be obtained by the method described below. As an example of a method of applying the negative electrode mixture to the negative electrode metal foil, a method of applying a dispersion solution of the constituent material of the negative electrode mixture onto the negative electrode metal foil can be mentioned.
An example of the coating thickness of the negative electrode mixture is about 40 μm on one side.

  The separator 13 is formed of, for example, a porous film made of a composite material of polypropylene (PP) and polyethylene (PE) having a thickness of 40 μm.

A substantially ring-shaped positive electrode current collecting member 25 is press-fitted on the inner peripheral side of the upper end portion of the hollow cylindrical shaft core 15. The positive electrode current collecting member 25 is made of, for example, aluminum.
All of the positive electrode tabs 16 of the positive electrode 11 are joined to the ring-shaped peripheral side surface of the positive electrode current collecting member 25 by ultrasonic welding or the like.

A substantially ring-shaped negative electrode current collecting member 20 is press-fitted and attached to the lower end portion of the shaft core 15. The negative electrode current collecting member 20 is made of, for example, copper.
The negative electrode tabs 17 of the negative electrode 12 are all joined to the ring-shaped peripheral side surface of the negative electrode current collecting member 20 by ultrasonic welding or the like.

A negative electrode conductive lead 21 made of nickel is fixed to the lower surface of the negative electrode current collecting member 20.
The negative electrode current collector lead 21 is joined to the negative electrode current collector member 20 by, for example, spot welding (resistance welding).
In addition, the negative electrode conductive lead 21 has a central portion, that is, a portion corresponding to the hollow portion of the shaft core 15 joined to the can bottom 2c of the battery can 2 by resistance welding or the like. For joining the negative electrode conductive lead 21 and the battery can 2, an electrode rod (not shown) is inserted into the hollow shaft of the shaft core 15, and the negative electrode conductive lead 21 is attached to the can bottom 2 c of the battery can 2 by the tip of the electrode rod. Press to do.

  A flexible positive electrode connection lead 26 formed by laminating a plurality of aluminum foils is joined to the upper surface of the positive electrode current collecting member 25 by ultrasonic welding or the like. The positive electrode connection lead 26 can flow a large current by laminating and integrating a plurality of aluminum foils, and is provided with flexibility.

A conductive connection plate 27 is disposed on the positive electrode current collecting member 25. The battery lid 3 is fixed to the periphery of the conductive connection plate 27 by caulking.
The conductive connection plate 27 is made of an aluminum alloy and has a substantially disk shape. Although not shown, a substantially circular safety valve that releases gas generated in the secondary battery 1 during overcharge is formed in the substantially central portion of the conductive connection plate 27. The safety valve is formed by a portion that is crushed so as to form a substantially V-shaped groove by pressing and is formed into a thin portion. On the lower surface of the conductive connection plate 27, the other end portion of the positive electrode connection lead 26 having one end portion bonded to the positive electrode current collecting member 25 is bonded by laser welding or the like.

A gasket 28 is provided to cover the peripheral edge of the conductive connection plate 27. The gasket 28 is made of, for example, a pull fluoroalkoxy fluororesin (PFA).
The battery lid 3 caulked to the peripheral edge of the conductive connection plate 27 is fixed to the battery can 2 together with the gasket 28 by caulking.
When the conductive connecting plate 27 with the battery lid 3 crimped is accommodated in the opening of the gasket 28 and the gasket 28 is pressure-bonded together with the peripheral edge of the opening 2b of the battery can 2 by pressing, as shown in FIG. Thus, a battery container in which the battery lid 3, the conductive connection plate 27, the gasket 28, and the battery lid 3 are integrated by caulking is produced.

A predetermined amount of non-aqueous electrolyte 5 is injected into the battery can 2. As an example of the nonaqueous electrolytic solution 5, it is preferable to use a solution in which a lithium salt is dissolved in a carbonate solvent. Examples of the lithium salt include lithium fluorophosphate (LiPF ₆ ), lithium fluoroborate (LiBF ₆ ), and the like. Examples of carbonate solvents include ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), methyl ethyl carbonate (MEC), or a mixture of solvents selected from one or more of the above solvents. Can be mentioned.

The electrode group 10 in which the negative electrode current collecting member 20 having the negative electrode conductive lead 21 bonded to the lower side of the shaft core 15 is press-fitted and the positive electrode current collecting member 25 is press-fitted to the upper side of the shaft core 15 is accommodated in the battery can 2. Then, the negative electrode current collecting lead 21 is joined to the can bottom 2 c of the battery can 2, and the nonaqueous electrolytic solution 5 is injected into the battery can 2.
Next, the positive electrode current collector 25 and the conductive connection plate 27 on which the battery lid 3 is caulked are connected by the positive electrode connection lead 26. Then, the secondary battery 1 illustrated in FIG. 1 is manufactured by caulking the conductive connection plate 27 and the battery lid 3 to the peripheral edge of the opening 2b on the upper side of the battery can 2 via the gasket 28. .

The secondary battery 1 is used after being charged to a predetermined charge level by a charging device.
A charge level shows the ratio remove | excluding the ratio of the amount of electricity discharged from the state in which the secondary battery was fully charged. The full charge indicates a 100% charge level or an upper limit value of the charge capacity set in consideration of a safety factor when charging from an external power source.
Here, when a secondary battery charged to a predetermined charge level was stored for a long time while maintaining the charge level, it was confirmed that the storage deterioration in the secondary battery differs depending on the charge level.
Hereinafter, this will be described with reference to measurement materials.

FIG. 3 and FIG. 4 show the experimental results of measuring the amount of power that can be extracted from the secondary battery using the charge level at the time of storage (hereinafter referred to as “stored charge level”) as a parameter.
In the experiment, the secondary battery 1 was stored while being charged periodically so that each stored charge level was maintained in a 25 ° C. environment for one year, and a change in electric energy before and after the storage was measured. The storage charge level was set to 100%, 90%, 80%, 70%, 60%, 50%, 20%, 0%.
The test shown in FIG. 4 was performed according to the following procedure. Before storage, after charging to the storage charge level and 100% charge level, when discharging at 5 times the current value obtained by dividing the rated capacity by the hour rate (hereinafter referred to as “5CA”) to the lower limit voltage of the operating voltage range The amount of power was measured. Thereafter, each stored charge level was stored for one year. After storage for one year, the battery was discharged again at 5 CA to the lower limit voltage of the working voltage range after being recharged to the storage charge level and 100% charge level as before storage, and the amount of power was measured.
The lower limit voltage of the operating voltage range was 2.7V. Incidentally, the end-of-charge voltage when the secondary battery 1 is fully charged in the initial state is 4.1V.

FIG. 3 is a characteristic diagram showing the relationship between the ratio of the amount of power that can be extracted before and after storage and each storage charge level. In FIG. 3, white circles indicate before storage, and black diamonds indicate after storage.
The procedure for obtaining experimental data will be specifically described by taking the case of the storage charge level of 90% in FIG. 3 as an example.
The secondary battery 1 is charged 90%. The amount of electric power when this secondary battery 1 is discharged at 5 CA up to 2.7 V is measured. The amount of power at this time was compared with the amount of power at the same 100% charge level, and the ratio was defined as the power amount ratio before storage at the storage charge level of 90%.

  The secondary battery 1 is stored for one year while being charged periodically so that the 90% charge level is maintained. And the electric energy at the time of charging to 90% charge level and discharging at 5CA to 2.7V is measured. The amount of electric power at this time was compared with the amount of electric power in the case of the 100% charge level performed before storage, and the ratio was defined as the electric energy ratio after storage at the storage charge level of 90%.

  Referring to FIG. 3, it can be seen that the higher the storage charge level, the greater the difference between the pre-storage charge amount and the post-storage charge amount. When the storage charge level is 20% or less, there is almost no difference between the charge amount before storage and the charge amount after storage. However, when the storage charge level is about 50% to 70%, the difference between the pre-storage charge amount and the post-storage charge amount tends to increase at a predetermined rate. Further, when the storage charge level exceeds 70%, the difference between the pre-storage charge amount and the post-storage charge amount tends to increase at a rate larger than a predetermined rate.

FIG. 4 is a characteristic diagram showing the relationship between the ratio of the amount of power that can be taken out before and after storage and the respective storage charge levels when 100% charged. In FIG. 4, white circles indicate before storage, and black diamonds indicate after storage.
In FIG. 4, the amount of electric power is expressed as a rate with the amount of electric power discharged from the 100% charge level before storage as 100%.
The procedure for taking experimental data will be specifically described by taking the case of the storage charge level 90% in FIG. 4 as an example.
The secondary battery 1 is charged 100%. In this state, the amount of electric power when discharged at 5 CA up to 2.7 V is measured. The power amount ratio at this time is displayed as a power amount ratio 100% before storage at a charge level 90% before storage. The power amount ratio of the pre-storage charge level is the same value as 100% for all the pre-storage charge levels.

  The secondary battery 1 is stored for one year while being charged periodically so that the 90% charge level is maintained. And the electric energy at the time of charging to 100% charge level and discharging at 5CA to 2.7V is measured. The amount of electric power at this time was compared with the amount of electric power before storage performed in the same manner, and the ratio was defined as the electric energy amount after storage at a storage charge level of 90%.

Referring to FIG. 4, the power amount ratio from the charge level exceeding 70% to 100% charge level after storage exists almost on the straight line A, and the power amount at the charge level of 70% or less after storage. It was found that the ratio is almost in the vicinity of the straight line B.
When the slopes of the straight lines A and B were calculated, the straight line A = −0.380 and the straight line B = −0.054. Further, the slope of the straight line A / the slope of the straight line B = 0.380 / 0.054≈7.0.

In other words, the experimental results indicate the following.
The ratio of the electric energy after storage with respect to the storage before storage decreases in a region where the storage charge level exceeds 70% to 100% (first charge level region) with a steep slope as indicated by a straight line A. In the region where the storage charge level is 70% or less (second charge level region), as shown by the straight line B, for example, about 1/7 as far as the first charge level region, Reduce with a small slope.

Next, the case where the secondary battery 1 was mounted in the electric vehicle was simulated.
FIG. 5 is a characteristic diagram showing the relationship between the travel distance of a vehicle equipped with a secondary battery stored at a predetermined charge level and each stored charge level. FIG. It is a characteristic view which shows the relationship between the travel distance of the vehicle carrying the secondary battery of the state charged%, and each preservation | save charge level.
In the case of a vehicle, in addition to the state of the battery such as the charge level, the travel distance per charge varies depending on the vehicle model, battery configuration, travel environment, and the like. In a vehicle equipped with the secondary battery 1, assuming that the electric energy and the travel distance shown in FIGS. 3 and 4 are in a proportional relationship and that it can travel 200 km per charge from the 100% charge level in the initial state, The distance that the vehicle can travel from the stored charge level is shown in FIG. It can be seen that the vehicle stored at the 0% storage charge level cannot travel as it is after storage and needs to be charged to travel. Conversely, a vehicle stored at a 100% storage charge level has the longest distance that it can travel after storage.

At first glance, it seems that it is convenient for the user because the vehicle that has been stored at the 100% storage charge level can travel as long as it is stored, but it seems to be convenient for the user, but in reality if the distance you want to travel before the next charge can be secured Further charging does not contribute much to the improvement of convenience. For example, when charging when returning home every day, it is not a problem whether or not a longer distance can be traveled if the travel distance for one day can be secured.
Looking at the daily mileage distribution of passenger cars actually running in Japan, the majority of drivers in Japan are less than 20km per day. In addition, if it is possible to travel 80 km, it means that over 75% of drivers are covered. Referring to FIG. 5, the travel distance 20 km is a distance that can be traveled at a 20% storage charge level, and even if the travel distance is 80 km, the travel distance can be traveled at a 50% storage charge level. Moreover, if it is 70% preservation | save charge level, about 120 km driving | running | working is possible.

  In other words, for the majority of users in Japan, as long as it is used normally, if it is charged every day and used, the mileage will be satisfied if the charge level is 20% or higher. In the case of 20% charge level, there is a possibility that the destination may not be reached when the vehicle is slightly detoured on the way back, or is slightly involved in traffic, or when the temperature is lowered and the efficiency is lowered. However, even if a storage charge level exceeding 70%, which is a storage condition with a large deterioration due to neglect, is not selected, the object can be sufficiently achieved even with a storage charge level of 70% or less.

On the other hand, there is a possibility that any user goes out by car for the purpose of traveling or the like. In that case, the mileage is secured by charging to 100% charge level before going out.
In that case, the effect of suppressing neglected deterioration appears in the travel distance after storage.
FIG. 6 shows the distance that can be traveled in a state of being charged to 100% charge level after being stored at each charge level for one year. From FIG. 6, it can be seen that the battery after storing for one year at the 50% charge level can travel 194 km, and the battery after storing for one year at the 70% charge level can travel 189 km. On the other hand, in a battery stored at 100% charge level for one year, the running distance remains at 167 km due to deterioration due to storage at a high charge level. If an attempt is made to travel a distance of 180 km, after storing for one year at a 100% storage charge level, charging is required on the way, and the user is required to charge halfway. If the user remembers that he was able to travel without charging 180 km in the initial stage, the user would strongly recognize the performance degradation.
5 and 6 show the travel distance calculated from the electric energy ratio on the vertical axis based on the experimental results shown in FIGS. 3 and 4, respectively.

FIG. 7 shows a block circuit diagram of a preferred embodiment of the charge control device 30 for the secondary battery configured based on the above experimental results. The charging control device 30 illustrated in FIG. 7 may be provided in an external power supply device except for the secondary battery module 31, or as a power supply system in the vehicle together with a control device that controls the secondary battery module except for the external power supply. It may be incorporated.
The secondary battery module 31 has a plurality of secondary batteries 1 as shown in FIG. In addition, the secondary battery module 31 includes a voltage detection unit 32 that detects the battery voltage of each secondary battery 1.

  The charging control device 41 has secondary battery information necessary for converting data such as a battery voltage transmitted from the voltage detection unit 32 of the secondary battery module 31 into a charge level. Moreover, the charge control apparatus 41 has the information regarding a normal charge level, and the charging means which charges each secondary battery 1 of the secondary battery module 31 to the upper limit of a predetermined charge level. This charging means can be controlled to charge up to at least the upper limit value of two different charging levels including the 100% charging level or the normal charging level. The normal charge level is a charge level that is automatically set by the charge control device 41 unless a charge level is selected or designated. In the following, the normal charge level is the 70% charge level shown in FIG.

The charge control device 41 switches between a 100% charge level and a normal charge level according to a selection signal transmitted from the selection switch 43. If another charge level is set in the charge control device 41, the charge level can be selected by the selection switch 43.
Further, the charging control device 41 has a charging period measuring unit 42. When the charge level exceeds a preset threshold value, the charging period measurement unit 42 measures a period in which the threshold value is exceeded.
And when the measured value by the charge period measurement part 42 exceeds predetermined value, the charge control apparatus 41 drives the discharge circuit 51, and each secondary battery 1 in the secondary battery module 31 is set to a normal charge level. To discharge. Thereby, even if each secondary battery 1 of the secondary battery module 31 is charged beyond the normal charge level and is not used for a long time, the charge of each secondary battery 1 is lowered to the normal charge level. Storage deterioration can be reduced. The threshold is a 70% charge level set as a normal charge level.

  When the charge level selected by the selection switch is higher than the normal charge level, the charge control device 41 drives the alarm device 52 to give a warning. The warning includes the fact that if the battery is stored for a long period of time in this state of charge, the deterioration of the battery is accelerated, or in addition, the travel distance of the vehicle is reduced. The warning can be given by display and / or report sound.

  The AC / DC converter 62 converts AC power supplied from an external power supply 61 such as a charging device into DC power when charging each secondary battery 1 of the secondary battery module 31. Moreover, when each secondary battery 1 of the secondary battery module 31 is discharged, it functions as an inverter that converts DC power discharged from each secondary battery 1 into AC power and supplies it to a load (not shown). To do.

Next, an embodiment of the secondary battery charge control method of the present invention will be described with reference to a process flow diagram shown in FIG.
In step S1, the external power source 61 and the secondary battery 1 are connected. As described above, the vehicle is mounted in the state of the secondary battery module 31, and the charge control device 41 manages the battery voltage of each secondary battery 1 and the total voltage of the entire secondary battery module 31 to control charging. Here, for the sake of simplicity and clarity, the charging control of each secondary battery 1 will be described.
In step S2, it is determined whether or not the connection between the external power source 61 and the secondary battery 1 has been made correctly. Although not shown in the figure, if the connection is not correct, the fact may be notified.

  When the connection between the external power source 61 and the secondary battery 1 is made correctly, a storage charge level (hereinafter simply referred to as “charge level”) is selected by the selection switch 43 in step S3. Although not shown, a process of notifying the user to select a charge level may be performed between step S2 and step S3. Alternatively, a plurality of charge levels may be displayed and a display screen for selecting a predetermined charge level by key input may be used.

An arbitrary number of charge levels can be set, but the area of the straight line A illustrated in FIG. 4, that is, the area where the charge level exceeds 70%, and the area of the straight line B, ie, the charge level is 70 It is important to set at least one from each region of% or less.
Here, it is assumed that three charge levels of 100% charge level, 70% charge level, and 50% charge level are set in advance in the charge control device 41 and can be selected by the selection switch 43. Further, as described above, the 70% charge level is set as the normal charge level.

  In step S4, the time from the start of the charge level selection in step S3 is measured, and it is determined whether or not a predetermined time has elapsed. If the charge level is not selected even after the predetermined time has elapsed (Yes in step S4), the normal charge level is set in step S5, and the process proceeds to step S11.

When the charge level is selected in step S3 (Yes), it is determined whether or not the charge level selected in step S6 is higher than the normal charge level. If the determination in step S6 is affirmative, the process proceeds to step S21. If the determination is negative, the process proceeds to step S11.
In this embodiment, since the normal charge level is 70% charge level, if the selected charge level is 100% charge level, the process proceeds to step S21, and the selected charge level is 70% charge level or 50% charge level. If so, the process proceeds to step S11.

  In step S11, it is determined whether or not the charging depth of the secondary battery 1 at the start of charging is lower than the selected upper limit value of the charging level. If affirmative in step S11, the process proceeds to step S12, and if negative, the process proceeds to step S14. In step S12, charging of the secondary battery 1 is started. The charging state of the secondary battery 1 is constantly monitored by the charging control device, and it is determined whether or not the upper limit value of the selected charging level has been reached in step S13. If step S13 is positive, that is, if the upper limit value of the selected charge level is reached, the process ends. If the result in step S11 is negative and the process proceeds to step S14, the process ends in step S14 after forcibly discharging to the upper limit value of the selected charge level.

That is, in the case of the 70% and 50% charge levels, the process proceeds from step S6 to step S11. In step S11, the charging depth of the secondary battery 1 at the start of charging is compared with the upper limit value of the selected charging level. When the 70% charge level is selected, the charge depth of the secondary battery 1 is 70% or less, and when the 50% charge level is selected, the charge depth of the secondary battery 1 is 50% or less. Are charged to the upper limit of each charge level in steps S12 and S13.
When the 70% charge level is selected, the charge depth of the secondary battery 1 exceeds 70%. When the 50% charge level is selected, the charge depth of the secondary battery 1 is 50%. If it exceeds the upper limit, in step S14, forcible discharge is performed to the upper limit value of each charge level, that is, 70% or 50%.

If affirmative in step S6 and proceed to step S21, a warning is given in step S21. In this warning, as described above, the selected charge level is a level that promotes storage deterioration of the secondary battery 1, and if the storage is continued for a long time in this charged state, the deterioration of the secondary battery proceeds quickly, and the vehicle The content is intended to reduce the travel distance.
When the warning ends, charging of the secondary battery 1 is started in step S22. At the same time, measurement of the charging period is started.

In step S23, it is determined whether or not full charge has been reached. That is, since the charge level affirmed in step S6 is a 100% charge level, the final charge level is full charge, and charging is performed until full charge is reached in steps S22 and S23.
In step S24, it is determined whether the charging period has exceeded a predetermined threshold period. The measurement of the charging period is continued as long as the external power supply 61 and the secondary battery 1 are connected, and is reset when the connection between the external power supply 61 and the secondary battery 1 is disconnected. That is, the vehicle is left unused without being used during the measured charging period. If the secondary battery 1 is stored in a state where the depth of charge exceeds 70% or in a fully charged state when the vehicle is not in use, storage deterioration is promoted as described above. Therefore, when step S24 is positive, the secondary battery 1 is forcibly discharged in step S25. The forced discharge is performed until the 70% charge depth that is the upper limit value of the normal charge level is reached.

In addition, it is recommended that the threshold value of the charging period is, for example, about 3 to 10 days.
In the above processing flow, the measurement of the charging period is started at the same time as the start of charging. However, the measurement of the charging period is started when the secondary battery reaches 70% depth of charge or full charge. Also good.
Further, although not shown in the above processing flow, it is desirable to notify that when charging is completed regardless of which charge level is selected.

As described above, according to the embodiment of the present invention, the following effects can be obtained.
(1) A first charge level belonging to a first charge level region (straight line A region in FIG. 4) in which storage deterioration of the secondary battery 1 in the storage state is large, and an upper limit value of the charge depth is fully charged; Select one of the second charge levels belonging to the second charge level region (straight line B region in FIG. 4) in which the storage deterioration is smaller than the charge level region of 1, and the upper limit value of the charge depth is smaller than the full charge. Can be charged.
For this reason, the speed of storage deterioration of the secondary battery 1 can be reduced.

(2) When the state of charge of the secondary battery 1 exceeds the upper limit value of the selected charge level, it is forcibly discharged to the upper limit value of the selected charge level, so that the stored charge level can be easily managed.
(3) If the fully charged state continues for a long time and exceeds a predetermined threshold value, it is forcibly discharged to the normal charge level, so even if there is a situation where the vehicle cannot be used or it is inadvertently left unattended for a long time The storage deterioration of the secondary battery 1 can be reduced.

(4) When the charge level is not selected at the time of charging, the charging control device 41 sets the normal charging level, so that the charging operation is simple and safe.
(5) When a charge level higher than the normal power reception level is selected, a warning that storage deterioration of the secondary battery 1 is promoted is given, so that it is possible to avoid unnecessary full charge.

  In the above embodiment, the upper limit value at the normal charge level is assumed to be 70%. However, the experimental data in FIG. 3 and FIG. 4 are created with an interval of the storage charge level of 10%, and considering the difference in the degree of deterioration after storage, etc., the upper limit value at the normal charge level It is not something that must be 70%. Even if the upper limit value at the normal charge level is about 65 to 75%, the same effect can be obtained.

  In FIG. 4, it is assumed that the relationship between the charge level and storage deterioration is greatly different between the two areas where the storage charge level exceeds 70% and the two areas where the storage charge level is 70% or less. However, the measurement data may be further subdivided and divided into three or more regions. In that case, it may be determined arbitrarily from which division area the normal charge level is selected in accordance with the performance of the vehicle.

  In the above-described embodiment, the lithium ion secondary battery is exemplified. However, the present invention can also be applied to other secondary batteries such as a nickel metal hydride secondary battery and a nickel cadmium secondary battery. That is, even when applied to a secondary battery other than a lithium ion secondary battery, the storage charge level is divided into a plurality of regions based on the rate of deterioration rate during storage, and the upper limit is fully charged. It is only necessary to select one of the second charge level and the second charge level that belongs to another region and whose upper limit value is smaller than the full charge so that charging can be performed.

In the one embodiment, the charge control device 30 is exemplified as the charge control circuit 30 including the discharge circuit 51 and the alarm device 52. However, the charge control device 30 may not include the discharge circuit 51 and / or the alarm device 52.
In addition, the present invention can be applied in various modifications within the scope of the gist of the present invention. In short, the change in the deterioration rate in the storage state with respect to the change in the charge level increases. At least one charge level belonging to the first and second charge level regions is set for a secondary battery having a first charge level region having a large change and a second charge level region having a small change. Any one of the charge levels can be selected and charged.

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Battery can 3 Battery cover 10 Electrode group 30 Charge control apparatus 31 Secondary battery module 32 Voltage detection part 41 Charge control apparatus 51 Discharge circuit 52 Alarm apparatus

Claims (11)

A first charge level region having a large change in the deterioration rate in the storage state with respect to a change in the charge level in the storage direction, and a change in the deterioration rate in the storage state with respect to the change in the charge level in the increase direction Is a charge control device for charging a secondary battery having a second charge level region smaller than the first charge level region,
A first charge level that belongs to the first charge level region and the upper limit value of the charge level is fully charged, and a second charge level that belongs to the second charge level region and has an upper limit value of the charge level that is smaller than the full charge. Charge level selection means for selecting one of the charge levels;
Charge level detection means for detecting the charge level of the secondary battery;
Charge control means for a secondary battery comprising charge control means for charging up to an upper limit value of each charge level selected by the charge level selection means.   2. The secondary battery charge control device according to claim 1, wherein the secondary battery is a lithium ion secondary battery, and the second charge level has an upper limit of 65 to 75% of a full charge. A charge control device for a secondary battery, characterized by being charged.   3. The secondary battery charge control device according to claim 1, wherein the second charge level is set as a normal charge level, and the selection unit does not select the first charge level and the second charge level. If not, the normal charge level is set by the charge control means.   The charge control device for a secondary battery according to any one of claims 1 to 3, further comprising: a deterioration rate in a storage state is increased when charging exceeds the upper limit value of the second charge level. A charging control device for a secondary battery, comprising warning means for informing the user.   5. The secondary battery charge control device according to claim 1, wherein the secondary battery has a charge level of the second charge in a state where the second charge level is selected. 6. A charge control device for a secondary battery, comprising: a discharge unit that discharges the secondary battery to the upper limit value of the charge level when an upper limit value of the level is exceeded.   In the charge control device for a secondary battery according to any one of claims 1 to 5, further, when the state of being charged exceeding the upper limit value of the second charge level is continued for a predetermined period, A charging control device for a secondary battery, comprising a discharging means for discharging the secondary battery.   A vehicle on which the charge control device for a secondary battery according to any one of claims 1 to 6 is mounted. A first charge level region having a large change in the deterioration rate in the storage state with respect to a change in the charge level in the storage direction, and a change in the deterioration rate in the storage state with respect to the change in the charge level in the increase direction Is a charge control method for charging a secondary battery having a second charge level region that is smaller than the first charge level region,
A first charge level that belongs to the first charge level region and the upper limit value of the charge level is fully charged, and a second charge level that belongs to the second charge level region and has an upper limit value of the charge level that is smaller than the full charge. A first step of selecting one of the charge levels;
A second step of detecting the charge level of the secondary battery;
And a third step of charging up to an upper limit value of each charge level selected by the charge level selection means.   The charge control method for a secondary battery according to claim 8, wherein the storage state is maintained when charging exceeds the upper limit value of the second charge level between the second step and the third step. A charge control method for a secondary battery, comprising a warning step for notifying that the deterioration rate of the battery becomes large.   The secondary battery charging control method according to claim 8 or 9, wherein the secondary battery is selected in a state where the second charging level is selected between the second step and the third step. A charge control method for a secondary battery, comprising: a discharging step of discharging the secondary battery to the upper limit value of the charge level when the charge level of the battery exceeds an upper limit value of the second charge level. 11. The secondary battery charge control method according to claim 8, further comprising: after the third step, a state in which the state of being charged exceeding the upper limit value of the second charge level is predetermined. A charge control method for a secondary battery, comprising: a discharge step of discharging the secondary battery when continued for a period of time.

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